Concrete

As easy to work as a child's mud pie, yet as strong as stone.

Derived from the Latin term 'concretus', meaning 'grow together', the development of concrete transformed Roman construction methods. The addition of 'pozzolana', a sandy black volcanic ash named after an area around the Bay of Naples, created a stronger paste which allowed for construction underwater, something crucial for bridge building. Concrete also allowed the construction of elaborate architectural features, such as curved columns and arches, the most notable examples of these being in the Pantheon in Rome.